In particular, the present invention refers to a printing device made in accordance with the preamble of the first claim. Such a device is already known, for example from patent publication EP 1977900.
One problem of known printing devices is to detect the position of the alignment marks arranged on the paper for suitable control of printing. For this purpose, using a photocell arranged along the path of the alignment mark is known. Nevertheless, the position of the alignment mark can vary from one type of paper to another. For this reason, the position of the photocell is, in general, adjustable, in a manual or motor-driven manner, to adapt the position of the photocell to the different positions of the alignment mark according to the type of paper. It is known, for example, to mount the photocell on a carriage that is slidable in a direction that is normal to the advancement direction of the paper. This solution is used, in particular, in the presence of a multi-supplying unit having several paper magazines, each with a different type of paper, supplied selectively to the print head according to the type of document to be printed.
In general, at each change of the type of paper, the photocell must be positioned at the point where the passage of the alignment mark is envisaged. This entails both a constructional complication because of the arrangement of the positioning system of the photocell and an operational complication because of the need to adjust the position of the photocell at each change of the type of paper.